Sisymbrium altissimum L. - Tumble Mustard
Family - Brassicaceae
Stems - To -1m tall, erect, herbaceous, branching in he apical 1/3, hispid in the basal 1/4, glabrous and glaucous above, from a big taproot, purplish at the nodes or not, slightly angled from decurrent petiole tissue.
Leaves - Alternate, petiolate, odd-pinnatifid. Lowest leaves with the rachis sparse hispid, petioles purplish at the base, green and glabrous apically. Divisions of the lower leaves +/-9 per side, subulate-lanceolate, coarsely toothed or not, hispidulous, often involute, 1-1.5cm long, +/-5mm broad, thinner near the base of the leaf. Terminal divisions broader than the laterals, not folded. All divisions acute. Upper cauline leaves reduced towards the apex. Divisions of the upper leaves linear, involute, glabrous, many with smaller divisions at their bases, to +2.5cm long, +/-1mm broad, acute, entire. Rachis of upper leaves glabrous to sparse hispidulous.
Inflorescence - Terminal and lateral racemes to +/-15cm long, compact in flower, elongating quickly in fruit, axis glabrous. Pedicels 7-8mm long in flower, to 1cm long and thickened in fruit, glabrous.
Flowers - Petals 4, spreading in the apical 1/2, white to yellow, spatulate, rounded at the apex, glabrous, tapering to a clawed base, 1cm long, 2-3mm broad at the apex. Stamens 6 (4 larger, 2 smaller), erect, exserted. Filaments to 5mm long, glabrous, translucent-white. Anthers -2mm long, erect and then spreading at dehiscence. Ovary cylindric, green, glabrous, to 6mm long in flower, superior, erect. Style wanting. Stigma capitate, two-lobed, 1.1mm broad. Sepals 4, spreading to erect, linear, 5-6mm long, involute, 1.3mm broad, glabrous, rounded and scarious at the apex, green. Fruits ascending, glabrous, to +/-8cm long, 1.1mm broad, angled, falcate, with a capitate (old stigma) apex.
Flowering - April - August.
Habitat - Fields, pastures, roadsides, railroads, sand y and rocky open ground.
Origin - Native to Europe.
Other info. - This species can be found scattered throughout Missouri. The plant can be identified by the filiform divisions of its cauline leaves and its fairly big flowers (can be yellow or white). The basal and lowest leaves of the plant have broader divisions and are very typical for the genus Sisymbrium.
Photographs taken at Eagle Bluffs Conservation Area, Boone County, MO., 5-3-04.